Chapter 14 - Alcohols

Question 1

What’s the functional group of alcohols?

Answer 1

-OH

Question 2

Are alcohols polar?

Answer 2

Yes, they have polar O-H bond because of difference in electronegativity of oxygen and hydrogen atoms

Question 3

What is volatility?

Answer 3

Measure of how easy a liquid is converted into a gas

Question 4

Why do alcohols have a lower volatility than alkanes?

Answer 4

Have a higher boiling point

Question 5

Why are the boiling points of alcohols greater than the boiling points of alkanes?

Answer 5

Strong hydrogen bonds between the O-H (polar) groups.

This requires more energy than overcoming the weaker london forces in alkanes.

Question 6

Why are alcohols soluble in water?

Answer 6

Form hydrogen bonds with water.

between polar OH groups

Question 7

Do alcohols get more or less soluble in water as the carbon chain increases in size?

Answer 7

-Less soluble.

As influence of the -OH group becomes relatively smaller

Question 8

What are the 3 ways alcohols are classed?

Answer 8

• Primary
• Secondary
• Tertiary

Question 9

What are primary alcohols?

Answer 9

• Alcohol where the -OH group is attached to a carbon atom that is attached to one alkyl group (and 2 hydrogens).
• e.g. ethanol

Question 10

What is a secondary alcohol?

Answer 10

• Alcohol where OH groups is attached to a carbon atom that is attracted to one hydrogen and 2 alkyl groups
• e.g. propan-2-ol

Question 11

What is a tertiary alcohol?

Answer 11

Alcohol where OH group is attracted to a carbon atom that is attracted to no hydrogen atoms and 3 alkyl groups.
e.g. 2-methylpropan-2-ol

Question 12

What is complete combustion?

Answer 12

Combustion in plentiful supply of oxygen

Question 13

What are the products formed in complete combustion of an alcohol?

Answer 13

carbon dioxide + water

Question 14

Give the equation for complete combustion of ethanol

Answer 14

C2H5OH(l) + 3O2(g) -> 2CO2(g) + 3H2O(l)

Question 15

Does the quantity of heat released per mole increase or decrease in combustion for longer chain alcohols?

Answer 15

Increases

Question 16

What is the oxidising agent mixture used for oxidising alcohols?

Answer 16

Solution of potassium dichromate (VI), K2Cr2O7, acidified with dilute sulphuric acid, H2SO4

Question 17

What does oxidising a primary alcohol by gently heating distillation form?

Answer 17

Aldehyde

Question 18

Describe process of oxidising a primary alcohol to form an aldehyde

Answer 18

Gently heat primary alcohol with potassium dichromate and sulphuric acid (oxidising agent) in distillation apparatus (volatile components can escape) to form aldehyde, which is the most volatile component (boils at lower temperature).

Question 19

Write the equation for oxidation of butan-1-ol

Answer 19

CH3CH2CH2CH2OH + [O] -> CH3CH2CH2CHO + H2O

Question 20

What does (oxidising) heating a primary alcohol under reflux form?

Answer 20

Carboxylic acid

Question 21

Describe the process of oxidising a primary alcohol to form a carboxylic acid

Answer 21

Heat primary alcohol with acidified potassium dichromate under reflux.
This forms an aldehyde but stays in reaction vessel with oxidising agent forming carboxylic acid. (volatile components can’t escape)

Question 22

Write equation for oxidation of primary alcohol, butan-1-ol, to form a carboxylic acid

Answer 22

CH3CH2CH2CH2OH + 2[O] -> CH3CH2CH2COOH + H2O

Question 23

What do secondary alcohols form when oxidised?

Answer 23

ketones

Question 24

What colour does a solution containing orange dichromate ions turn when reduced?

Answer 24

Green

Question 25

Describe oxidation of a secondary alcohol to form a ketone

Answer 25

Heat alcohol mixed with acidified potassium dichromate under reflux, forming ketone

Question 26

Give equation for oxidation of propan-2-ol

Answer 26

CH3CHOHCH3

Question 27

What do tertiary alcohols form when oxidised?

Answer 27

They don't oxidise

Question 28

What is dehydration of an alcohol? What is the product of this? What type of reaction is this?

Answer 28

- When a water molecule is removed from a starting material (alcohol) - Forms an alkene - Elimination

Question 29

Describe the process of dehydration of an alcohol

Answer 29

Alcohol heated under reflux in presence of an acid catalyst such as concentrated phosphoric acid, H3PO4. Producing an alkene

Question 30

Give equation for dehydration of cyclohexanol

Answer 30

(CH2)5CHOH -> C6H12 + H20

Question 31

Describe the process of forming a haloalkane to from an alcohol

Answer 31

Alcohol heated under reflux with sulphuric acid and sodium halide. Sulphuric acid reacts with sodium halide to form hydrogen halide, which reacts with alcohol to form haloalkane.

Question 32

What kind of reaction is the formation of haloalkane from an alcohol?

Answer 32

Substitution

Question 33

Write the overall equation for reaction of propan-2-ol with H2SO4 and NaBr

Answer 33

CH3CHOHCH3 +NaBr +H2SO4 -> CH3CHBrCH3 + NaSO4 +H2O

Question 34

What is formed when a carboxylic acid and an alcohol are heated under reflux in presence of acid catalyst

Answer 34

Ester

Question 35

How do you name an ester?

Answer 35

Use alcohol stem and put -yl at the end and use carboxylic acid stem and add -oate. e.g. methyl ethanoate

Question 36

What is required for fermentation, producing an alcohol?

Answer 36

Yeast and aqueous solution of sugar (glucose)

Question 37

What is produced in fermentation of glucose?

Answer 37

Carbon dioxide and ethanol

Question 38

Give equation for fermentation of glucose?

Answer 38

C6H12O6(aq) -> 2C2H5OH(aq) + 2CO2(g)